24 vs 36

One comment I can make of the D5200 vs the D600 is that I don't see any real world differences at low ISOs. At ISO 3200 and 100% the D600 wins of course but with a little noise reduction with neat image and reducing the size to 50% there is very little difference. Comparing to my old D90 there is a huge difference. For me the D7100 will be a nice upgrade. One day the D7100 can be my back up when I finally go FF. I also did my comparisons with 1-3 stops of exposure boost and about 25% - 100% shadow boost in LR. Much better than the D90 -D300 generation of sensors but about 1.5 stops short of the FF sensors (just ball park figures) which can take up to 4 stops of shadow boost without much breakdown.

At 36mp and at ISO 3200 the D800 is Pretty noisy as well unless you downsize it, and if your going to do that you might as well compare the D5200 after downsizing as well. Take any of these files down to 12mp and compare to the previous generation sensors and you can see the improvement in noise, detail and sharpness. Weak or no AA filtration only really matters at or near 100% viewing. If your a heavy cropper or print very large than the D600/800 are the tickets.